Hi all
I also know we need RMAN to take backup for ASM . But i also seen its possible to take backup by using dd command itself on ASM . Why we need RMAN rather than this method . What is the specific reason we using RMAN,

1. You'll run into the classic "fractured block" issue when attempting a recover or reading a block after the restore
2. RMAN can be used to
a relocate individual datafiles,
b duplicate / clone database,
c restore to an alternate server,
d copy / move from ASM to filesystem
e verify for corruption
f generate reports on backups taken
None of which dd of ASM will do reliably (depending on the skills of the DBA/SA).